a) Field of the Invention
The invention concerns mains units for voltage conversion for electronic terminal devices. The invention concerns in particular a plug-in socket for coupling to corresponding standard plugs and for connecting an electrical terminal device to a voltage supply. The invention also concerns means for voltage conversion for a plug-in socket.
b) Description of the Related Art
Voltage converters in the form of what are referred to as mains units have been known for some time. They convert a primary voltage (for example a mains voltage) into a secondary voltage. In a wide-spread form those mains units are disposed in a separate housing and connected to the mains network by means of a cable. A further cable connects the mains unit and the terminal device to be supplied.
In another wide-spread form as is known for example from laid-open EP 0 085 802 A1 the mains unit has a housing which is fixedly connected to the housing of a mains plug.
DE 93 208 93 U1 discloses a mains plug with incorporated mains unit, a so-called plug mains unit. The electronic system for converting a primary voltage into a secondary voltage is disposed with other electronic components on a circuit board.
DE 42 27 629 A1 also discloses a mains plug for the connection of electrical terminal devices. In order to dissipate the heat loss from voltage transformation away from the plug housing it is proposed that the plug pins are used for cooling purposes.
Wolski, Gerhard B: Komplettes Netzteil in einem Chip. EN: DE/Der Elektromeister+deutsches Handwerk. 1990, DE 22/90, pages 1673, 1674, 1679 describes a complete mains unit which is implemented in a single chip.
Mains units are therefore known in which the voltage converter is disposed in a separate housing outside the item of equipment to be supplied. Electrical coupling to the mains network as well as electrical coupling of the terminal device which is to be supplied are effected by means of separate electric lines.
Mains units are frequently also embodied in the form of part of the electronic device system. They are disposed for example on the same printed circuit board as the rest of the electronic components of the terminal device. Mains units are also known which are specifically suitable for use in computers. They are disposed in their own housing which in turn is incorporated into the housing of the terminal device to be supplied. Those mains units are not hermetically sealed and in addition involve artificial convection, for example they have a possible way of dissipating waste heat, for example by way of slots and their own electrical ventilation.
When using separate mains units, for example in the configuration of a plug mains unit, but also in relation to the mains units in a separate housing within a larger housing of the terminal device, considerable limitations in terms of operating comfort and convenience and a high level of complication and expenditure in terms of installation and contacting of those mains units with the mains network have to be accepted. External mains units which have cable connections on both sides also considerably restrict the level of convenience of use. A problem which frequently occurs is that the weight of the mains unit which in fact is arranged centrally in the cable pulls on the cable in such a way that either the plug connection to the terminal device comes loose or the terminal device can even be pulled down off a support and destroyed.